Process for the production of sharp-edge fibers



Oct. 31, 1967 A. L. BREEN 3,350,488

PROCESS FOR THE PRODUCTION OF SHARP-EDGE FIBERS Original F-iled May 27,1958 2 Sheets-Sheet 1 I A. L. BREEN Oct. 31', 1967 PROCESS FOR TEE PRODOriginal Filed May 27, 1958 2 sheet$-sheet 2 United States Patent Ofi3,350,488 PROCESS FOR THE PRODUCTION OF SHARP-EDGE FIBERS Alvin LeonardBreen, Wilmington, Del., assignor to E. I. du Pont de Nemours andCompany, Wilmington, Del., a corporation of Delaware Originalapplications May 27, 1958, Ser. No. 738,166, and June 7, 1962, Ser. No.200,758, now Patent No. 3,188,689, dated June 15, 1965. Divided and thisapplication Mar. 3, 1965, Ser. No. 436,888

4 Claims. (Cl. 264-171) This 200,75 No. 3,188,689 and of cation Ser. No.738,166, filed May 27, 1

This invention relates to the man of a novel cross-section.

Much effort has be of fabrics th abandoned appli- 958. ufacture offilaments The desirability of producing textile filaments having one ormore sharp longitudinal edges for obtaining silklike fabrics has longbeen recognized. Despite numerous proposals mainly drawn to extrusionorifice designs, it has not been feasible to aments having sharp edgesin cross-section by the extrusion of melts or solutions of fiber-formingpolymers. This is due to the fact that the surface of a filament formedan orifice tends to assume the cross a circle, the smallest boundaryforth al area.

One object of this invention is to produce filaments of polymershaving-one or more sharp longi- -sectional contour of e givencross-sectiontudinal edges.

A further object is the preparation of a fabric that has the propertiesof silk. Other objects will become apparent in the course of thefollowing discussion.

In accordance with one embodiment of the invention a composed ofsegments of at least two dissimilar synthetic tions, said cross-sectionhaving at least aid polymers, any conthe filament may beseparated intoits component n. Alternatively, all sections as in a plane orcurvilinear triangle; or a multiplicity of sharp points such as in afigure formed by the joining of 2 or more simple segments as in a formeecross. Y

FIGURE 1 shows in axial section a spinneret assembly useful for thispurpose. Front or bottom plate 1 with ori- 3350A Patented Oct. 31, 1S

lice

fices 2 is recessed at the back about plateau -like prot at the bottomof back rotational positioning of th FIGURE 2 shows a reduced view ofthe plan of th 25 front plate. Appearing in this view are four plateaus,eacl into its component sections by m 65 components should have lowadhesi on to each othenQbusly this is not necessary where one componentof the r is to be removed by dissolution or chemical decom- .ition.Because of their commercial availability, ease processing and excellentproperties, the condensation ymers and copolymers, e.g., polyamides,polysuliamides and polyesters and particularly those that can readilymelt spun are preferred for application in s method. Suitable polymerscan be found for instance long the fiber-forming polyamides and thepolyesters rich are described in such patents as US. Patents )71,250,2,071,253, 2,130,523, 2,130,948, 2,190,770 and 465,319. The preferredgroup of polyamides comprises )ly(hexamethylene adipamide), poly(hexamethylene bacamide), poly(epsilon-caproamide) and the co- Jlymersthereof. Suitable polyesters, besides poly(ethyl- 1e terephthalate), arethe corresponding copolymers )ntaining sebacic acid, adipic acid,isophthalic acid as ell as the polyesters containing recurring unitsderived om glycols with more than two carbons in the chain, .g.,diethylene glycol, butylene glycol, decamethylene lycol andtrans-bis-1,4-(hydroxy methyl)-cyclohexane.

Other groups of polymers useful as components in llaments of the presentinvention can be found among he polyurethanes, the polyureas, celluloseesters and :ellulose ethers as well as among the polyvinyl com- ;oundsincluding such polymers as polyethylene, polyicrylonitrile, polyvinylchloride, polyvinylidene chloride, polyvinyl alcohol, and copolymerscontaining the monomers of these polymers and similar polymers asdisclosed in US. Patents 2,601,256, 2,527,300, 2,456,360 and 2,436,926.

When it is desired to remove all sections composed of one polymercomposition by dissolution, a solvent for such polymer is selected thatwill not dissolve or have an adverse effect on sections composed ofother polymer compositions. Thus in Example I which appears below,formic acid was used to remove the polyamide sections from the filamenthaving both polyester and polyamide sections in its cross-section. Theextent of dissolution of the soluble portion can be controlled asdesired.

Similarly, all sections composed of one polymer composition can beremoved by chemical decomposition. Thus polyester sections of apolysegmented filament having alternate polyester and polyamidesections, would be degraded by treatment with hot caustic as would thecopolyamide or polyurea portions of polysegmented filaments havingcopolyamide-polyacrylonitrile or polyureapolyacrylonitrile alternatingsections by treatment with mineral acids.

In the examples, the relative viscosity (1 i.e., viscosity of a solutionof polymer relative to that of the solvent is used as a measure of themolecular weight. The polyamide solutions contained 5.5 g. of polymer in50 ml. of 90% formic acid and the viscosity was measured at 25 C. Thepolyester solutions contained 2.15 g. of the polymer in ml. of 7/10mixture of tetrachlorophenyl/phenol and the viscosity was measured at 30C.

Example I A spinneret similar to that shown in FIGURES 1 to 3 with 17orifices was constructed. The plateau 4 was Vs in. in diameter and in.high. The counterbore 22 Was 40 mils in diameter and extended to within48 mils of the face of the spinneret. The capillary 21 had a diameter of12 mils. The lead hole 31 in the upper plate 7 was in. in diameter wasdrilled to within 94 mils of the bottom of plate 7. The upper orifices32 were 9 mils in diameter and were drilled on a circle having a 39.5mil radius the center of which was concentric with the upper lead holeand with the plateau in the orifice in the lower plate. The spinneretwas assembled with a 3 mil thick shim 16.

Poly(hexamethylene adipamide) of a 36 was fed to chamber 9 of thespinneret and extruded to form the triangular segments of the filamentand poly(ethylenc terephthalate) of 33 containing 0.3% of TiO was fed toannulus 8 and then through orifices 32 to form the formee cross segmentof the filaments cross-section. The two molten polymers were extruded inthe ratio of 9.5/ 10.0 by volume respectively at 290 C. and the yarnwound up at 1000 y.p.m. The yarn was drawn 4 (that is, to 400% of itsoriginal length) over an 88 C. pin and then passed over a 140 C. plateto reduce shrinkage. A cross-section of a typical filament is shown inFIGURE 7. The yarn had a tenacity of 3.9 g.p.d., an Mi (initial modulus,grams per denier) of 53, an ultimate elongation of 32% and a totaldenier of 50.

The yarn was knitted into a tubing which was quite lean in appearanceand had poor visual covering power. The tubing was treated for 3 hourswith 98% formic acid in a Soxhlet extractor, removed, rinsed with waterand dried. Despite the loss of about 50% of the fiber weight bydissolution of the polyamide sections the visual covering power of thetubing was greatly increased. The extracted tubing had a soft silk-likehandle and was scroopy. The cross-section of filaments remaining in theextracted fabric resembled a formee cross as shown in 108 of FIGURE 7.

Example 11 Using the same spinneret as in Example I, poly(ethy1- eneterephthalate) of 17, 26.9 containing 0.3% of TiO; was fed to chamber 8of the spinneret and extruded as the segments of a composite filamentdesignated 101 in FIGURE 4 while poly(hexamethylene adipamide) of m. 36was fed to chamber 9 and extruded as the segments of a compositefilament designated 102 in FIGURE 4. The polymers were extruded at 290C. and the yarn wound up at 400 y.p.m. The yarn was drawn 43X over a 98C. pin. The resulting yarn had a tenacity of 4.1 grams per denier, andinitial modulus of 56 and had a denier per filament of 8.3. A portion ofthe drawn yarn was wound on a perforated metal bobbin and immer'sed incold 98% formic acid for 3 hours. After rinsing and drying the residualpolyester yarn had a tenacity of 3.8 g.p.d., a Mi of 73, an ultimateelongation of 28% and a total denier of 80 for the 68 filaments thenpresent. typical cross-section of a filament is shown in 109 of FIGURE8.

A portion of the original yarn was woven into a 2 X 2 twill fabrichaving 120 yarns per inch in the warp an 84 yarns per inch in thefilling. The resulting fabric was immersed in 98% formic acid forminutes until the poly(hexamethylene adipamide) sectors were dissolvedfrom the composite filaments. The fabric possessed all of the propertiesof a silk fabric as liveliness and drape, the subtle scroop of silk, thehandle, the low denier per filament, the high modulus and good recoveryproperties.

A repetition of the above spin with positions of the 2 polymers changedgives filaments which after treatment with formic acid leavesfillet-shaped sectors of the polyester similar to segment 102 of FIGURE4.

Example III The following example illustrates the differentcrosssections obtained by varying the volume of polymers delivered tovarious sectors of the composite filaments Using the spinneret ofExample I with a three mil shim, poly(ethylene terephthalate) of n, 28.1containing 2.0% of TiO was fed to chamber 8 of the spinneret and poly-(ethylene terephthalate) of n, 31 fed to chamber 9. The polymers wereextruded at 290 C. and the yarn wound up at 1000 y.p.m. The volume ofthe two polymers entering the composite filaments were varied byadjustment of their respective constant displacement pumps. In the firstspin the volumes of the pigmented polymer to the non-pigment polymer was1:1 and filaments were obtained having cross-sections similar to thatshown in FIG- URE 4. When the ratio of pigmented to bright polymer wasset at 4/16, filaments with cross-sections similar to acetate portionsof the filaments and leaves small dt FIGURE 5 were obtained. When thepumps were adfilaments of polyacrylonitrile of shape similar to justedto give a ratio of 16/4. as above cross-sections URE 8.

similar to FIGURE 6 were obtained. The composite filaments have beenproduced in The above spins are repeated replacing the unpigmented 5examples by the melt spinning technique. Obvioi polyester with thecopolyester poly[ethylene/poly(ethylother spinning methods likeplasticized melt spinn ene oxide) glycol terephthalate] with acomposition of dry spinning, wet spinning, can be employed successfi80/20 by weight, the poly(ethylene oxide) glycol units In some instancesparticularly when the melting beha having a molecular weight of 6000.Upon immersing the or the solubility of the co yarns in a hot 5%solution of NaOH the segments cor- 10 would not permit spinningresponding to 102, 104, 106 in FIGURES 4, 5 and 6 are methods, acombination of dissolved and residual cross-sections of poly(ethyleneused. Thus, for instance, one component, can be spun h h l correspondingt 101, 103, 105 i FIG- a solution in a high boiling solvent or as aplasticized m URES 4, 5, and 6 remain in the respective yarns. While theother component is extruded as a mol l5 polymer In these instances, thesolvents or plasticizt Example IV may be wholly or partially removedsubsequently, pr erably by washing them out by the help of low boiliUsing the apparatus and polymers of Example I the l m positions of thetwo polymers were reversed. The polyester and polyamide were extruded at290 C. at a ratio of 12/ 16 by volume respectively and the compositefilaments Wound P at 5 00 Y-P- The Y Was drawn X in the art that byaltering the shape of the orifice 21, tl

Over a P A typical cross-Section of the drawn nal cross-section can becontrolled to a certain exter filament is shown in FIGURE 9. A portionof a yarn was Al h h in cross-section which resemble a square withrounde edge of a glass microscope slide under a tension of about 0 0.5g.p.d. so that the yarn suffered a 90 change of direc- The compositefilaments illustrated in this inventit 20 have substantially roundcross-sections before separatit of the components. However, it will beapparent to tho st r and polyamlde segments 80 that the y Was othermodificatlons of the composite filaments and henci Posed 0f filamentsWhlch 1H Cross-86611011 resembled 1 of the shape of the residualfilaments after dissolutior and 111 of FIGURE 9. 5 can be altered bychanging the number and placement The filaments in the above drawn yarnwere completely f t of 48 y p m using 2 cu ft of r P mlnllte at p S 1are extruded through the upper orifices 32 and over the to operate thejet. plateau. Alteration of the viscosities of the component A portionof the above drawn yarn not exposed to polymers affects theconfiguration obtained A low v1sacetone or fragmented was wound on aperforated metal cosity polymer tends to be pushed mward more readilytube and placed in 98% formic acid at the boiling point by the flow forminutes. The tube and yarn was then placed in cold the shape of thesegment th formic acid for an additional 15 minutes, rinsed withwaration 1n the component filaments is also aflected by the ter anddried The residual polyester filaments which in interfacial tension andthe individual tendencies of the cross-section resembled segment 110 ofFIGURE 9 had polymers to wet the spinneret surfaces a tenacity of 3 6 gpd an ultimate elongation of 31% a Although the spmneret used in theexamples 1s a con M1 of 68 and a denier per filament of 1 O..The yarnwas venient apparatus for the preparation of the filaments of used as afilling face in the weaving of a satin with yarn t is invention it Wlllbe obvious to those skilled in the of round cross-section, poly(ethyleneterephthalate), as art that other spinnerets can be used. Otherspinnerets a warp. The fabric had a dry, crisp, silk-like handle acrosspermit the production of filaments or ribbons having althe filling bandbut was less silk-like than the fabric of ternating segments 112 and 113as shown in FIGURE 10 Example 11. which can be split or dissolved apartto give sharp-edged Example V filaments.

The process of this invention affords a convenient Using the apparatusand polymers s in Ex mpl V, means of obtaining filaments having one ormore sharp composite filaments are extruded and the continuousfilapoints i cross section d of a lower d i h can b ments wound up at5000 y.p.m. The yarn is dipped in otherwise attained Thus, the inventionpermits the proacetone and then drawn Over a P at The gduction ofsharp-edged filaments having a denier of 0 1 to ments of polyester breakand split during the drawing so 10 or larger. Its greatest utility,however, is in the range that a yarn somewhat resembling spun staple isobtained in of 0.1 to 5 denier per filament The novel filaments canwhich the cruciform-like filaments of polyamide in crossbe used toobtain all manner of new and novel effects section have short lengths ofpolyester microfibers atin fabric handle, scroop, appearance andcovering power tached to a surface which pro ect beyond the original pe-Y P p 561660139 0f the P y COmPOSIfiOH and riphery of the filaments.mentary cross-section.

The invention is to be limited only by the scope of the Example VIfollowing claims.

I claim:

Solutions of polyacrylonitrile and cellulose acetate 1. A method ofmaking sharp-edged filaments which both in dimethylformamide are dryspun from the spincomprises spinning a composite filament ofsubstantially neret of Example I. The resulting filaments incross-section uniform cross-section composed of segments of at leasthave alternate segments of the two polymers with a crentwo dissimilarsynthetic polymeric compositions, said ulated periphery. An acetate bathdissolves the cellulose 7 cross-section having at least two segments ofat least one aid polymers, any contact between such'segments ofReferences Cited same polymer being substantially point contact andUNITED STATES PATENTS rating a sharp-edged filament therefrom. Theprocess of claim 1 wherein said separation is :532 JmPhShCd by 52,815,532 12/1957 Braunlich 18--8 The process of claim 1 wherern saidsepara'uon 18 omplished by dissolution of all segments composed FOREIGNPATENTS 211,133 11/1957 Australia.

Jne polymeric composition. 1. The process of claim 1 wherein saidseparation is acnplished by chemical degradation of all segments com- 10ALEXANDER MERKEL, Primar Examiner. sed of one polymer composition. H. W.LUCKOWER, I. H. WOO, Assistant Examiners,

1. A METHOD OF MAKING SHARP-EDGED FILAMENTS WHICH COMPRISES SPINNING ACOMPOSITE FILAMENT OF SUBSTANTIALLY UNIFORM CROSS-SECTION COMPOSED OFSEGMENTS OF AT LEAST TWO DISSIMILAR SYNTHETIC POLYMERIC COMPOSITIONS,SAID CROSS-SECTION HAVING AT LEAST TWO SEGMENTS OF AT LEAST ONE OF SAIDPOLYMERS, ANY CONTACT BETWEEN SUCH SEGMENTS OF THE SAME POLYMER BEINGSUBSTANTIALLY POINT CONTACT AND SEPARATING A SHARP-EDGED FILAMENTTHEREFROM.